Synthetic fibers with enhanced stain resistance and methods of making the same

ABSTRACT

Synthetic fibers with enhanced stain resistance, yarns and carpets prepared from these fibers and compounds and methods for their production are provided.

FIELD OF INVENTION

The present disclosure relates to synthetic fibers with enhanced stainresistance, articles prepared from these fibers and methods for theirproduction.

BACKGROUND

Polyamides are used in a variety of applications and often includeadditives used to modify physical properties including, but not limitedto viscosity, tensile strength, fire resistance, stain resistance,flowability, color and texture. Many of these additives can be difficultto work with for various reasons, such as volatility, moistureabsorptivity, photosensitivity and thermal sensitivity and subsequentdegradation processes, and melt viscosity incompatibility. Accordingly,use of such additives on a commercial scale can be inefficient,resulting in production of polyamides with inferior physical properties.

In one application, polyamides are used to faun fibers in textiles suchas fabrics, carpets and rugs. These fibers oftentimes suffer from a lackof stain resistance, due to chemical interactions of acidic sites in thepolyamides and complementary sites in staining compositions. Thesechemical interactions typically fix stains on a substrate, and makestain removal difficult. Accordingly, it is known in the art to addstain blocking additives to the polyamide composition, in order toincrease its stain resistance by a reduction in the chemicalinteractions, thereby making removal of the stains easier, and moreefficient.

Known stain blocking additives added to polyamides during polymerizationinclude sulfoisophthalic acids, sulfobenzoic acids, and sulfonic acids.However, these agents are typically hygroscopic, oftentimes agglomeratewhen used on a commercial scale, and can clog industrial reactors thusleading to production inefficiencies, cost increases, and formation ofinferior fibers.

While different approaches such as use of powdered stain blockingagents, spray solutions of stain blocking agents and physicaldistribution of stain blocking agents via masterbatch compounds inpolyamide melts have been developed, each of these approaches stillsuffers from production inefficiencies and forms fibers that can stillbe improved.

Polyesters have commonly been used in the past as the carrier polymer ofa masterbatch compound. There are numerous problems, however, when amasterbatch having polyester, particularly polyethylene terephthalate(PET) as the carrier polymer is combined with polyamides such aspolycaprolactam, also known as nylon 6 or N6. First, PET has a meltingpoint (m.p. 252-260° C.) which is higher than N6 (m.p. 215-220° C.).This difference in polymer melting point and the associated differencesin melt phase polymer flow causes process issues that complicateextrusion, transfer of extrudate to a spinneret, fiber formation, andfiber draw. Additionally, above a given use rate, PET will undergomacrophase separation when used with N6, which will cause fibrillationof PET in the fiber. PET is also comparatively expensive when used as abase masterbatch component.

Alternatively, N6 can be used as a carrier in a masterbatch composition.Should that masterbatch then be used in combination with an N6 polymerbase, concerns associated with melting point and polymer melt phase flowwould be effectively mitigated, because the base fiber forming polymerand the masterbatch carrier polymer would be the same. However, as isunderstood by those skilled in the art, N6 requires careful control ofits moisture content prior to melt spinning into filament. Inadequatecontrol of moisture content can cause major process issues. For example,a N6 masterbatch with excessive moisture content will cause a drop inthe melt viscosity of the polymer melt during melt spinning, thus makingit difficult to draw fiber from the extruder. This issue can be resolvedby an additional polymer drying, or conditioning step, before the N6masterbatch is fed to an extruder or by the removal of moisture or othervolatiles during the melt spinning process. The removal of moisture orvolatiles is taught in a number of patents, including U.S. Pat. No.6,537,475 B1, U.S. Pat. No. 6,753,385 B2, and U.S. Pat. No. 6,861,480B2. Additional patents include U.S. Pat. No. 6,117,550, U.S. Pat. No.6,420,044, U.S. Pat. No. 6,433,107, U.S. Pat. No. 7,115,224, U.S. Pat.No. 6,680,018, U.S. Pat. No. 6,635,346, U.S. Pat. No. 6,334,877, andU.S. Pat. No. 6,589,466.

U.S. Pat. No. 8,501,898, also herein incorporated by reference,discloses a method of adding a masterbatch that includes a stainblocking ingredient, into a reactor during the polymerization ofcaprolactam monomer to N6. The masterbatch is added into the reactor,prior or during polymerization, for the purpose of incorporating thestain blocking ingredient into N6.

SUMMARY OF THE INVENTION

An aspect of the present disclosure relates to a synthetic fibercomprising a first fiber forming polymer, a second polymer having a meltpoint that is lower than the melt point of the first fiber formingpolymer, and a stain blocking additive.

In one nonlimiting embodiment, the first fiber forming polymer is apolyamide, a polyester, a polyolefin, or a combination thereof. Inanother nonlimiting embodiment, the first fiber forming polymer is nylon6.

In one nonlimiting embodiment, the second polymer is a polyolefin. Inanother nonlimiting embodiment the second polymer is an unmodifiedpolyolefin. In one nonlimiting embodiment, the second polymer ispolypropylene.

In one nonlimiting embodiment, the stain blocking additive is anaromatic sulfonate or an alkali metal salt thereof. In anothernonlimiting embodiment, the stain blocking additive is5-sulphoisophthalic acid, sodium salt (NaSIPA).

Another aspect of the present disclosure relates to yarns formed fromthese synthetic fibers.

Another aspect of the present disclosure relates to a fabric knittedfrom these synthetic fibers and yarns.

Another aspect of the present disclosure relates to carpet formed fromthese yarns.

Another aspect of the present disclosure relates to a process forforming a synthetic fiber with enhanced stain resistance. The processcomprises forming a melt from a first fiber forming polymer and amasterbatch. The masterbatch compound comprises a second polymer havinga melt point lower than the melt point of the first fiber formingpolymer and a stain blocking additive. The first fiber fanning polymeris present in a range from about 80 to 98 percent by weight and themasterbatch compound is present in a range from about 2 to 20 percent byweight. A synthetic fiber with enhanced stain resistance is thereafterformed from the polymer melt.

In one nonlimiting embodiment, the synthetic fiber with enhanced stainresistance is formed from the polymer melt by extruding the melt througha spinneret to form one or a plurality of filaments, quenching thefilament or filaments, drawing the filament or filaments, and windingthe filament or filaments onto a tube.

In one nonlimiting embodiment of this process, the masterbatch compoundhas a moisture content of less than about 200 ppm.

In one nonlimiting embodiment of this process, the masterbatch compoundis not dried or conditioned prior to forming the polymer melt.

In another nonlimiting embodiment of this process, no additional step isrequired to remove volatiles while forming the polymer melt.

In one nonlimiting embodiment of this process, the first fiber formingpolymer is a polyamide, polyester, polyolefin or combination thereof. Inanother nonlimiting embodiment, the first fiber forming polymer is nylon6.

In one nonlimiting embodiment of this process, the second polymer is apolyolefin. In another nonlimiting embodiment the second polymer is anunmodified polyolefin. In one nonlimiting embodiment, the second polymeris polypropylene.

In one nonlimiting embodiment of this process, the stain blockingadditive is an aromatic sulfonate or an alkali metal salt thereof. Inanother nonlimiting embodiment, the stain blocking additive is5-sulphoisophthalic acid, sodium salt.

Another aspect of the present disclosure relates to yarns formed fromthe synthetic fibers produced by this process.

Another aspect of the present disclosure relates to fabrics knitted fromthe synthetic fibers and yarns formed from this process.

Another aspect of the present disclosure relates to carpet formed fromthe yarns formed from this process.

Another aspect of the present disclosure relates to a process forforming a nylon 6 fiber with enhanced stain resistance. The processcomprises forming a polymer melt from a nylon 6 polymer and amasterbatch compound. The masterbatch compound comprises a secondpolymer having a melting point that is lower than the melting point ofthe first fiber forming polymer, and a stain blocking additive. Thenylon 6 polymer is present in a range from about 80 to 98 percent byweight, and the masterbatch compound is present in a range from about 2to 20 percent by weight. A nylon 6 fiber comprising one or a pluralityof filaments having enhanced stain resistance is formed from the polymermelt.

In one nonlimiting embodiment of this process, the masterbatch compoundhas a moisture content less than about 200 ppm.

In one nonlimiting embodiment of this process, the masterbatch compoundis not dried or conditioned prior to forming the polymer melt.

In one nonlimiting embodiment of this process, no additional step isrequired to remove volatiles while forming the polymer melt.

Another aspect of the present disclosure relates to yarns formed fromthe nylon 6 fibers produced by this process.

Another aspect of the present disclosure relates to fabrics knitted fromthe nylon 6 fibers and yarns formed from this process.

Another aspect of the present disclosure relates to carpets and rugsformed from the yarns formed from this process.

Yet another aspect of the present disclosure relates to a masterbatchcompound. The masterbatch compound comprises a thermoplastic carrier anda stain blocking additive, and has a moisture content less than about200 ppm.

In one nonlimiting embodiment, the thermoplastic carrier is present inthe masterbatch compound in a range from about 20 to 80 percent byweight.

In one nonlimiting embodiment, the stain blocking additive is present inthe masterbatch compound in a range from about 20 to 80 percent byweight.

In one nonlimiting embodiment of this process, the second polymer is apolyolefin. In another nonlimiting embodiment the second polymer is anunmodified polyolefin. In one nonlimiting embodiment, the second polymeris polypropylene.

In one nonlimiting embodiment, the stain blocking additive in themasterbatch is an aromatic sulfonate or an alkali metal salt thereof. Inanother nonlimiting embodiment, the stain blocking additive is5-sulphoisophthalic acid, sodium salt.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows results of a stain test comparing fabrics knitted fromsynthetic fibers prepared in accordance with Examples 1, 2, 3 and 4.

FIG. 2 shows results of a stain test comparing fabrics knitted fromsynthetic fibers prepared in accordance with Examples 5, 6, 7, 8 and 9.

DETAILED DESCRIPTION OF THE INVENTION

Provided by this disclosure are synthetic filaments and fibers withenhanced stain resistance, yarns, fabrics and carpets prepared fromthese fibers, and methods and masterbatch compounds for theirproduction.

The synthetic fiber of the present disclosure comprises a first fiberforming polymer. Examples of first fiber forming polymers which can beused include, but are not limited to, polyamides, polyesters,polyolefins and combinations thereof.

Suitable polyamides include fiber forming polyamides known in the art tobe suitable for the formation of bulked continuous filament fibers,having sufficient viscosity, tenacity, chemical stability andcrystalinity to be at least moderately durable in such application. Thepolyamide may be selected from the group consisting of nylon 5,6; nylon6/6; nylon 6; nylon 7; nylon 11; nylon 12; nylon 6/10;, nylon 6/12;nylon DT; nylon 6T; nylon 6I; and blends or copolymers thereof. In oneembodiment the polyamide is nylon 6,6 polymer.

In one embodiment, the first fiber forming polymer comprises is nylon 6.

Suitable polyolefins include polypropylene. Suitable polyesters includefiber forming polyesters known in the art. The polyester resin may beselected from the group consisting of polyethylene terephthalate,polytrimethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate, polylactic acid (PLA) and blends or copolymers thereof.

In one nonlimiting embodiment, the first fiber forming polymer ispresent in the synthetic fiber in a range from about 80 to 98 percent byweight. In another nonlimiting embodiment, the first fiber formingpolymer is present in the synthetic fiber in a range from about 80 to98.8 percent by weight.

The synthetic fiber of the present disclosure further comprises a secondpolymer having a melting point that is less than the melting point ofthe first fiber forming polymer. It is preferred that the presence ofthe second polymer does not cause the synthetic fiber to fibrillate.Examples of second polymers useful in the present disclosure include,but are not limited to polyolefins, polylactic acid, polystyrene, or ablend or copolymer thereof. In one nonlimiting embodiment, thepolyolefin is an unmodified polyolefin. In another nonlimitingembodiment, the second polymer is polypropylene.

In one nonlimiting embodiment, the second polymer is present in thesynthetic fiber in a range from about 1 to about 10 percent by weight.In another nonlimiting embodiment, the second polymer is present in thesynthetic fiber from about 1 to about 5 percent by weight. In anothernonlimiting embodiment, the second polymer is present in the syntheticfiber from about 0.1 to about 10 percent by weight.

The synthetic fiber of the present disclosure further comprises a stainblocking additive. Suitable stain blocking additives include those thatdisable acid dye sites. For example, in polyamides, such as Nylon 6,6 orNylon 6, acid dyes sites refer to amine end groups or amide linkageswhich react or associate with acid dyes which result in staining. Stainblocking additives react or associate with these acid dye sites toprevent the acid dye sites from reacting or associating with acid dyes.Suitable stain blocking additives for use in polyamides are discussed inU.S. Pat. No. 5,155,178, herein incorporated by reference. Suitablestain blocking additives include, but are not limited to aromaticsulfonates and alkali metal salts thereof, such as 5-sulfoisophthalicacid, sodium salt and dimethyl-5-sulfoisophthalate, sodium salt. In onenonlimiting, embodiment, the stain blocking additive is5-sulfoisophthalic acid, sodium salt (NaSIPA).

In one nonlimiting embodiment, the stain blocking additive is present inthe synthetic fiber in a range from about 1 to about 10 percent byweight. In another nonlimimting embodiment, the stain blocking additiveis present in the synthetic fiber in a range from about 1 to about 5percent by weight. In another nonlimimting embodiment, the stainblocking additive is present in the synthetic fiber in a range fromabout 0.1 to about 5 percent by weight.

The present disclosure also relates to yarns prepared from the syntheticfibers, as well as fabrics and carpets prepared from the syntheticfibers and/or yarns.

Also provided by this disclosure is a process for forming a syntheticfiber with enhanced stain resistance. The process comprises forming apolymer melt from a first fiber forming polymer and a masterbatchcompound. The polymer melt can be formed by any known method in the art.In one nonlimiting embodiment, the polymer melt is formed in a meltextruder. A fiber or filament is then formed from the polymer melt.

In one nonlimiting embodiment, fibers may be prepared by using knownmelt spinning process technology. With such technology, the polymer meltis provided to a spinning machine. The polymer melt is forwarded by ametering pump to a filter pack, and through a spinneret plate containingcapillary orifices of a shape chosen to yield the desired filamentcross-section at the spinning temperature. These cross-sectional shapesknown in the art can include circular, non-circular, trilobal, andhollow shapes. Typical hollow filaments can be produced as disclosed inU.S. Pat. No. 6,855,425. Spinning temperatures can range from about 270°C. to about 300° C. The bundle of filaments emerging from the spinneretplate is cooled by conditioned quench air, treated with spin finish (anoil/water emulsion), and optionally interlaced, e.g. using aninterlacing air jet to form a yarn.

Suitable polymers for use as the first fiber forming polymer includethose that can be used to form synthetic fiber. Examples of first fiberforming polymers useful in this process include, but are not limited to,polyamides, polyesters, polyolefins and combinations thereof.

Suitable polyamides include fiber forming polyamides known in the art tobe suitable for the formation of bulked continuous filament fibers,having sufficient viscosity, tenacity, chemical stability andcrystalinity to be at least moderately durable in such application. Thepolyamide may be selected from the group consisting of nylon 5,6; nylon6/6; nylon 6; nylon 7; nylon 11; nylon 12; nylon 6/10;, nylon 6/12;nylon DT; nylon 6T; nylon 6I; and blends or copolymers thereof. In oneembodiment the polyamide is nylon 6,6 polymer.

Suitable polyolefins include polypropylene. Suitable polyesters includefiber forming polyesters known in the art. The polyester resin may beselected from the group consisting of polyethylene terephthalate,polytrimethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate, polylactic acid (PLA) and blends or copolymers thereof.

In one nonlimiting embodiment, the first fiber forming polymer is nylon6.

In one nonlimiting embodiment, the first fiber forming polymer ispresent in a range from about 80 to 98 percent by weight. In anothernonlimiting embodiment, the first fiber forming polymer is present in arange from about 80 to about 98.8 percent by weight.

The masterbatch compound used in the process comprises a second polymerhaving a melt point which is lower than the melt point of the firstfiber foaming polymer. In nonlimiting embodiments, the combination offirst polymer and masterbatch does not produce a synthetic fiber that isprone to fibrillation. Examples of second polymers useful in the presentdisclosure include, but are not limited to polyolefins, polylactic acid,polystyrene, or a blend or copolymer thereof. In one nonlimitingembodiment, the polyolefin is an unmodified polyolefin. In anothernonlimiting embodiment, the second polymer is polypropylene.

The masterbatch compound used in this process further comprises a stainblocking additive. Suitable stain blocking additives include those thatdisable acid dye sites. For example, in polyamides, such as Nylon 6,6 orNylon 6, acid dyes sites refer to amine end groups or amide linkageswhich react or associate with acid dyes which result in staining. Stainblocking additives react or associate with these acid dye sites toprevent the acid dye sites from reacting or associating with acid dyes.Suitable stain blocking additives for use in polyamides are discussed inU.S. Pat. No. 5,155,178, herein incorporated by reference. Suitablestain blocking additives include, but are not limited to aromaticsulfonates and alkali metal salts thereof, such as 5-sulfoisophthalicacid, sodium salt and dimethyl-5-sulfoisophthalate, sodium salt. In onenonlimiting, embodiment, the stain blocking additive is5-sulfoisophthalic acid, sodium salt (NaSIPA).

In one nonlimiting embodiment, the masterbatch compound is present infiber in a range from about 2 to about 20 percent by weight. In anothernonlimiting embodiment, the masterbatch compound is present in fiber ina range from about 0.2 to about 20 percent by weight.

In one nonlimiting embodiment, the moisture content of the masterbatchcompound is less than about 200 ppm. In another nonlimiting embodiment,the moisture compound content of the masterbatch is less than about 100ppm. In yet another nonlimiting embodiment, the moisture content of themasterbatch compound is less than about 50 ppm.

The absence of moisture or volatiles is important to allow for propermelt processing of the polymer melt to effectively form a syntheticfiber. Drying or conditioning of the feedstocks, including themasterbatch compound, requires additional costs, processing steps andprocessing time. Conditioning, as is known by those skilled in the art,is a process of allowing the feedstock or masterbatch compound to reachhygroscopic equilibrium with its surrounding atmosphere. Frequently,conditioning is performed using an anhydrous gas, such as nitrogen, toachieve lower moisture content in a material such as pelletizedmasterbatch, polymer, fiber, or yarn, for example. Through undueexperimentation, it was found that the masterbatch compound of thepresent disclosure does not require drying or conditioning prior toforming the polymer melt to achieve this moisture content. In onenonlimiting embodiment of the current disclosure, no drying orconditioning step is required to lower the moisture content of themasterbatch compound before forming the polymer melt.

U.S. Pat No. 6,537,475, U.S. Pat No. 6,753,385 and U.S. Pat No.6,861,480, incorporated herein by reference, require additional steps toremove moisture or volatiles during fiber formation. For example, if anextruder is used to form the polymer melt, one or more vents may beneeded to facilitate the removal of moisture or volatiles. In addition,the devolatization or moisture removal may be assisted through the useof vacuums along with the extruder or with injection of a gas, such asnitrogen, through the extruder vents. Other methods of removing moistureor volatiles include drying or conditioning of the feedstocks, theaddition of water-scavenging additives, or a combination of thesemethods. Through undue experimentation, it was found that with the useof the first fiber forming polymer and the masterbatch compound ofcurrent disclosure, no additional steps are required to remove moistureor volatiles while forming the polymer melt. This provides a significantcost and time savings over the processes taught in the prior art.Therefore, in nonlimiting embodiments of the current disclosure, noadditional step is required to remove volatiles while forming thepolymer melt.

In one nonlimiting embodiment, the synthetic fibers produced by thisprocess preferably comprise about 1 to about 10% by weight of the secondpolymer. In another nonlimiting embodiment, the synthetic fibersproduced by this process preferably comprise about 1 to about 5% byweight of the second polymer. In another nonlimiting embodiment, thesynthetic fibers produced by this process preferably comprise about 0.1to about 10% by weight of the second polymer.

In one nonlimiting embodiment, the synthetic fibers produced by thisprocess also preferably comprise about 1 to about 10% by weight of astain blocking additive. In another nonlimiting embodiment, thesynthetic fibers produced by this process also preferably comprise about1 to about 5% by weight of a stain blocking additive. In anothernonlimiting embodiment, the synthetic fibers produced by this processalso preferably comprise about 0.1 to about 10% by weight of a stainblocking additive.

The present disclosure also relates to yams prepared from syntheticfibers produced by this process, as well as fabrics and carpets preparedfrom the synthetic fibers and/or yams.

Also provided by the present disclosure is a process for forming a nylon6 fiber with enhanced stain resistance. This process comprises forming apolymer melt of a nylon 6 polymer and a masterbatch compound, thenspinning synthetic fiber according to the aforementioned melt spinningprocesses to form a nylon 6 fiber with enhanced stain resistance fromthe polymer melt.

The masterbatch compound used in the process comprises a second polymerhaving a melt point which is lower than the melt point of the firstfiber forming polymer. In nonlimiting embodiments, the combination offirst polymer and masterbatch does not produce a synthetic fiber that isprone to fibrillation. Examples of second polymers useful in the presentdisclosure include, but are not limited to polyolefins, polylactic acid,polystyrene, or a blend or copolymer thereof. In one nonlimitingembodiment, the polyolefin is an unmodified polyolefin. In anothernonlimiting embodiment, the second polymer is polypropylene.

The masterbatch compound used in this process further comprises a stainblocking additive. Suitable stain blocking additives include those thatdisable acid dye sites. For examples, in polyamides, such as Nylon 6,6or Nylon 6, acid dyes sites refer to amine end groups or amide linkageswhich react or associate with acid dyes which result in staining. Stainblocking additives react or associate with these acid dye sites toprevent the acid dye sites from reacting or associating with acid dyes.Suitable stain blocking additives for use in polyamides are discussed inU.S. Pat. No. 5,155,178, herein incorporated by reference. Suitablestain blocking additives include, but are not limited to aromaticsulfonates and alkali metal salts thereof, such as 5-sulfoisophthalicacid, sodium salt and dimethyl-5-sulfoisophthalate, sodium salt. In onenonlimiting, embodiment, the stain blocking additive is5-sulfoisophthalic acid, sodium salt (NaSIPA).

In one nonlimiting embodiment, the moisture content of the masterbatchis less than about 200 ppm. In another nonlimiting embodiment, themoisture content of the masterbatch is less than about 100 ppm. In yetanother nonlimiting embodiment, the moisture content of the masterbatchis less than about 50 ppm. In one nonlimiting embodiment this process,the masterbatch compound is not dried or conditioned prior to formingthe polymer melt. In another nonlimiting embodiment of this process, noadditional step is required to remove volatiles while faulting of thepolymer melt.

In one nonlimiting embodiment, the nylon 6 polymer is present in a rangefrom about 80 to about 98 percent by weight and the masterbatch compoundis present in a range from about 2 to about 20 percent by weight. Inanother nonlimiting embodiment, the nylon 6 polymer is present in arange from about 80 to about 98.8 percent by weight and the masterbatchcompound is present in a range from about 0.2 to about 20 percent byweight.

The present disclosure also relates to yarns prepared from the nylon 6fibers produced by this process, as well as fabrics and carpets preparedfrom the nylon 6 fibers and/or yarns.

Also provided by the present disclosure is a masterbatch compound. Themasterbatch compound comprises a thermoplastic carrier. Examples ofthermoplastic carrier useful in the masterbatch include, but are notlimited to polyolefins, polylactic acid, polystyrene, or a blend orcopolymer thereof. In one nonlimiting embodiment, the thermoplasticcarrier is present in the masterbatch compound in a range from about 20to about 80 percent by weight. In one nonlimiting embodiment, thepolyolefin is an unmodified polyolefin. In another nonlimitingembodiment, the second polymer is polypropylene.

The masterbatch compound further comprises a stain blocking additive.Suitable stain blocking additives include those that disable acid dyesites. For example, in polyamides, such as Nylon 6,6 or Nylon 6, aciddyes sites refer to amine end groups or amide linkages which react orassociate with acid dyes which result in staining. Stain blockingadditives react or associate with these acid dye sites to prevent theacid dye sites from reacting or associating with acid dyes. Suitablestain blocking additives for use in polyamides are discussed in U.S.Pat. No. 5,155,178, herein incorporated by reference. Suitable stainblocking additives include, but are not limited to aromatic sulfonatesand alkali metal salts thereof, such as 5-sulfoisophthalic acid, sodiumsalt and dimethyl-5-sulfoisophthalate, sodium salt. In one nonlimiting,embodiment, the stain blocking additive is 5-sulfoisophthalic acid,sodium salt (NaSIPA).

The masterbatch compound may further comprise other additives, to beused to confer additional benefits to articles upon polymer meltextrusion and melt spinning Examples of such additives are inorganicpigments, and ultraviolet (UV) light absorbers or optical brighteningagents. Examples of inorganic pigments are titanium dioxide, bariumsulfate, carbon black, manganese dioxide, and zinc oxide. Examples of UVlight absorbers or optical brightening agents are2,2′-(1,2-ethenediyldi-4,1 phenylene)bisbenzoxazole, availablecommercially by Eastman Chemical Company under the tradename Eastobrite®OB-1, and 2,2′-(2,5-thiophenediyl)bis(5-tert-butylbenzoxazole, availablecommercially by Mayzo, Inc. under the tradename Benetex® OB.

In one nonlimiting embodiment, the moisture content of the masterbatchcompound is less than about 200 ppm. In another nonlimiting embodiment,the moisture content of the masterbatch compound is less than about 100ppm. In yet another nonlimiting embodiment, the moisture content of themasterbatch compound is less than about 50 ppm.

The following section provides further illustration of the syntheticfiber and fabrics knitted of this invention as well as comparativefibers and fabrics knitted therefrom. These working examples areillustrative only and are not intended to limit the scope of theinvention in any way.

TEST METHOD Acid Stain Test

Acid dye stain resistance is evaluated using a procedure adapted fromthe American Association of Textile Chemists and Colorists (AATCC)Method 175-2003, “Stain Resistance: Pile Floor Coverings.” 9 wt % ofaqueous staining solution is prepared, according to the manufacturer'sdirections, by mixing cherry-flavored KOOL-AID® powder (Kraft/GeneralFoods, Northfield, Ill. White Plains, N.Y., a powdered drink mixcontaining, inter alia, FD&C Red No. 40). A knitted sock (4×6-inch) isplaced on a flat non-absorbent surface. A hollow plastic 2-inch (5.1 cm)diameter cup is placed tightly over the test sample, which can be aknitted sock, or a tufted carpet, for example. Twenty ml. of theKOOL-AID® staining solution is poured into the cup and the solution isallowed to absorb completely into the test sample. The cup is removedand the stained sample is allowed to sit undisturbed for 24 hours.Following incubation, the stained sample is rinsed thoroughly under coldtap water, excess water is removed by centrifugation, and the sample isdried in air. The sample was visually inspected and rated for stainingaccording to the FD&C Red No. 40 Stain Scale described in AATCC Method175-2003. Stain resistance is measured using a 1-10 scale. Anundetectable test staining is accorded a value of 10.

EXAMPLES

Comparative Examples 1 and 2 and Examples 3 and 4 were produced usingpilot scale machine. The pilot equipment included a 12″ single screwextruder having five heating zones, a filter screen pack, any of aselection of desired spinnerets, a fiber quenching zone, godet rolls,and winders.

Example 1 Comparative Example—No Masterbatch

A 920 denier, 64 filaments N6 bulked continuous filament (BCF) was madeon the pilot scale machine. Pigments of various colors were mixed with aN6 polymer product made by BASF, Ultramid® B27 E 01. The pigments and N6were mixed at the screw feeder. Fibers were spun with no process breaks.This BCF yarn had a light earth tone color. It was knitted into a sockand tested for stain resistance according to the Acid Dye Stain Test.This sock rated 1 out of 10, and so failed the Acid Dye Stain Test.

Example 2 Comparative Example—NaSIPA/N6 Masterbatch

This example was similar to Example 1, except a masterbatch was added tothe flake feeder in addition to the pigments. This masterbatch was amelt blend of NaSIPA with N6 (Ultramid® B27 E 01) at a 50/50 ratio byweight. The masterbatch was not dried or conditioned prior to use. Therate of masterbatch addition at the screw feeder was 6 weight percent.The addition of the NaSIPA/N6 masterbatch drastically reduced thepolymer melt viscosity, and made the spinning process inoperable.

Example 3 NaSIPA/Polypropylene Masterbatch

Instead of the masterbatch as used in Example 2, a NaSIPA/polypropylenemasterbatch (50/50 weight % blend) was used in this example inaccordance with the present invention. The masterbatch was not dried orconditioned prior to use. Although some reduction in polymer viscositywas observed at 6 wt. % masterbatch addition rate, the spinning processwas manageable. Light earth tone color solution dyed N6 BCF wassuccessfully produced. A sock was knitted from the BCF and tested forstain resistance according to the Acid Dye Stain Test. The sock passedthe stain test (rating 9 out of 10).

Example 4 Dimethyl-5-Sulfoisophthalate, Sodium Salt/PolypropyleneMasterbatch

Instead of the masterbatch as used in Example 2, adimethyl-5-sulfoisophthalate, sodium salt/polypropylene masterbatch(50/50 weight % blend) was used in this example in accordance with thepresent invention. The dimethyl-5-sulfoisophthalate, sodium salt is soldby Mytech Inc. The masterbatch was not dried or conditioned prior touse. The rate of addition of the masterbatch to the N6 polymer was 6weight percent. The viscosity drop was significantly less than example3. The spinning process was good. Light earth tone color solution dyedN6 BCF was successfully produced. A sock was knitted from the BCF andtested for stain resistance according to the Acid Dye Stain Test. Thestain rating was 7.5 which was significantly better than example 1 withno masterbatch addition.

Example 5 NaSIPA/Polypropylene Masterbatch

This example was similar to Example 3 except the masterbatch additionrate was raised from 6 to 10 percent. It was also knitted into a sock,and tested for stain resistance according to the Acid Dye Stain Test.The sock passed the stain test (10 out of 10).

Example 6 Dimethyl-5-Sulfoisophthalate, Sodium Salt/PolypropyleneMasterbatch

This example was similar to Example 4 except the masterbatch additionrate was raised from 6 to 10 percent. It was also knitted into a sock,and tested for stain resistance according to the Acid Dye Stain Test.The stain rating was 8.5, which was significantly better than example 1.

Comparative Examples 7 and 11 and Examples 8, 9 and 10 were produced ona prototypic single position machine with roll speeds and productivitysimilar to commercial spinning machines. The nylon 6 polymer used forthe Examples 7 through 11 was a bright polymer produced by BASF(Ultramid® B27 E 01). The resin had 2.7 +/− 0.3 relative viscosity (ISO307) and was conditioned to have a moisture content of approximately 500ppm. The polymer temperature before the spinning pack was controlled atabout 265 +/− 1° C.). The spinning throughput was eighty pounds (80lbs.) per hour.

The polymer was extruded through the spinnerets and divided into two (2)sixty-eight filament (68) segments. The molten fibers were then rapidlyquenched in a chimney, where cooling air at about 10° C. was blown pastthe filaments at four hundred and fifty cubic feet per minute [450 dm]through the quench zone. The filaments were then coated with a lubricantfor drawing and crimping. The coated yams were drawn at 2422 yards perminute (2.9× draw ratio) using a pair of heated draw rolls. The drawroll temperature was 160° C. The filaments were then forwarded into adual-impingement hot air bulking jet, similar to that described in Coon,U.S. Pat. No. 3,525,134, teachings of which are herein incorporated byreference, to form two 1350 denier, 20 denier per filament (dpf) BCFyarns. The temperature of the air in the bulking jet was 180° C.

The spun, drawn, and crimped BCF yarns were knitted into socks andheat-set on a Suessen heat-setting machine at setting temperature of185° C. The holdup time in the setting zone was about 60 seconds. Theheatset socks were tested for stain resistance according to the Acid DyeStain Test.

Example 7 Comparative Example—No Masterbatch

For this example, color pigments were mixed with N6 polymer at the screwfeeder. The spinning process was good, with no process breaks. This BCFyarn had a light earth tone color. The test sample was knitted intosock, heatset in a Suessen chamber and tested for stain resistanceaccording to the Acid Dye Stain Test. It failed the stain test with therating of 5 in a 1 to 10 rating scale.

Example 8 Example—NaSIPA/Polypropylene Masterbatch

A masterbatch that consisted of color pigments, NaSIPA and polypropylenecarrier was used to make this example. The NaSIPA loading in thismasterbatch was approximately 50 weight percent. About 2 weight percentof the masterbatch was mixed with Nylon 6 polymer at the screw feeder.The spinning process was similar to Example 7. This BCF yarn also had alight earth tone color identical to Example 7. The test sample wasknitted into sock, heatset in a Suessen chamber, and tested for stainresistance according to the Acid Dye Stain Test. It was rated 7.5. Interms of stain resistance, the BCF yarn was better than the yarn made inExample 7, but this yarn still underperformed.

Example 9 Example—NaSIPA/Polypropylene Masterbatch

This example was similar to Example 8, except the masterbatch loadingwas increased from 2 to 3 weight percent. The Suessen heat-set sock wastested for resistance according to the Acid Dye Stain Test. It was rated9.0, which is considered as passing the Acid Dye Stain Test.

Example 10 Example—NaSIPA/Polypropylene Masterbatch

This example was similar to Example 8, except the masterbatch loadingwas increased from 3 to 4 weight percent. This example had a mediumearth tone color. It was knitted into sock, heat set in a Suessenchamber, and tested for stain resistance according to the Acid Dye StainTest. It was rated 9.5, which is considered as passing the Acid DyeStain Test.

Example 11

Comparative Example with no Masterbatch

This example was similar to Example 7, except the pigment loading wasincreased to match the color of Example 10. The finished carpet wastested for stain resistance according to the Acid Dye Stain Test. It wasrated 5.0, which is considered as not passing the Acid Dye Stain Test.

1. A synthetic fiber comprising: a) a first fiber forming polymerpresent in a range from about 80 to 98 percent by weight b) a secondpolymer present in a range from about 1 to 10 percent by weight, whereinthe second polymer has a melt point which is lower than the melt pointof the first fiber forming polymer; and c) a stain blocking additivepresent in a range from about 1 to 10 percent by weight.
 2. Thesynthetic fiber of claim 1, wherein the presence of the second polymerdoes not cause the synthetic fiber to fibrillate.
 3. The synthetic fiberof claim 1, wherein the first fiber forming polymer is selected from thegroup consisting of a polyamide, polyester, polyolefin and combinationsthereof.
 4. The synthetic fiber of claim 1, wherein the first fiberforming polymer is nylon
 6. 5. The synthetic fiber of claim 1 whereinthe second polymer is present in a range from about 1 to 5 percent byweight.
 6. The synthetic fiber of claim 1 wherein the second polymer isa polyolefin, polylactic acid, polystyrene, or a blend or copolymerthereof.
 7. The synthetic fiber of claim 1, wherein the second polymeris an unmodified polyolefin.
 8. The synthetic fiber of claim 1 whereinthe second polymer is polypropylene.
 9. The synthetic fiber of claim 1,wherein the stain blocking additive is present in a range from about 1to 5 percent by weight.
 10. The synthetic fiber of claim 1, wherein thestain blocking additive is an aromatic sultanate or an alkali metal saltthereof.
 11. The synthetic fiber of claim 10, wherein the stain blockingadditive is 5-sulphoisophthalic acid, sodium salt.
 12. A yarn formedfrom the synthetic fiber of
 13. A fabric knitted from the syntheticfiber of claim
 1. 14. A carpet formed from the yarn of claim
 12. 15. Aprocess for forming a synthetic fiber with enhanced stain resistance,said process comprising the steps of: a) forming a polymer melt of afirst fiber forming polymer and a masterbatch compound, wherein themasterbatch compound comprises a second polymer having a melting pointwhich is less than the melting point of the first fiber forming polymer,and a stain blocking additive, wherein the first fiber forming polymeris present in a range from about 80 to 98 percent by weight, and themasterbatch compound is present in a range from about 2 to 20 percent byweight; and b) forming a synthetic fiber with enhanced stain resistancefrom the polymer melt.
 16. The process of claim 15, wherein themasterbatch compound has a moisture content less than about 200 ppm. 17.The process of claim 15, wherein the masterbatch compound has a moisturecontent less than about 50 ppm.
 18. The process of claim 15, wherein themasterbatch compound is not dried or conditioned prior to forming thepolymer melt.
 19. (canceled)
 20. The process of claim 15, wherein thepresence of the second polymer does not cause the synthetic fiber tofibrillate.
 21. The process of claim 15, wherein the first fiber formingpolymer is selected from the group consisting of a polyamide, polyester,polyolefin and combinations thereof.
 22. The process of claim 15,wherein the first fiber forming polymer is nylon
 6. 23. The process ofclaim 15, wherein the second polymer is present in the masterbatchcompound in a range from about 20 to 80 percent by weight.
 24. Theprocess of claim 15, wherein the stain blocking additive is present inthe masterbatch compound in a range from about 20 to 80 percent byweight.
 25. The process of claim 15, wherein the second polymer ispresent in the synthetic fiber in a range from about 1 to 10 percent byweight
 26. The process of claim 15, wherein the second polymer ispresent in the synthetic fiber in a range from about 1 to 5 percent byweight.
 27. The process of claim 15, wherein the second polymer is apolyolefin.
 28. (canceled)
 29. The process of claim 15, wherein thesecond polymer s polypropylene.
 30. The process of claim 15, wherein thestain blocking additive is present n the synthetic fiber in a range fromabout 1 to 10 percent by weight.
 31. The process of claim 15, whereinthe stain blocking additive is present in the synthetic fiber in a rangefrom about 1 to 5 percent by weight.
 32. The process of claim 15,wherein the stain blocking additive is an aromatic sulfonate or analkali metal salt thereof.
 33. The process of claim 32, wherein thestain blocking additive is 5-sulphoisophthalate, sodium salt.
 34. Theprocess of claim 15, wherein forming a synthetic fiber furthercomprises: a) extruding said polymer melt through a spinneret to formone or a plurality of filaments, and b) drawing the fiber.
 35. A yarnformed from the process of claim
 15. 36. A fabric knitted from thesynthetic fiber produced from claim
 15. 37. A carpet formed from theyarn of claim
 35. 38. A rug formed from the yarn of claim
 35. 39. Amasterbatch compound comprising: a thermoplastic carrier; and a stainblocking additive, wherein the moisture content of the masterbatchcompound is lower than about 200 ppm.
 40. The masterbatch compound ofclaim 39, wherein the masterbatch compound has a moisture content lessthan about 50 ppm.
 41. The masterbatch compound of claim 39, wherein thethermoplastic carrier is present in the masterbatch compound in a rangefrom about 20 to 80 percent by weight.
 42. The masterbatch compound ofclaim 39, wherein the stain blocking additive is present in themasterbatch compound in a range from about 20 to 80 percent by weight.43. The masterbatch compound of claim 39, wherein the thermoplasticcarrier is a polyolefin.
 40. (canceled)
 45. The masterbatch compound ofclaim 39, wherein the thermoplastic carrier is polypropylene.
 46. Themasterbatch compound of claim 39, wherein the stain blocking additive isan aromatic sulfonate or an alkali metal salt thereof.
 47. Themasterbatch compound of claim 39, wherein the stain blocking additive is5-sulphoisophthalic acid, sodium salt.
 48. The masterbatch compound ofclaim 39, further comprising a component selected from the groupconsisting of inorganic pigments, optical brightening agents,ultraviolet light stabilizers, and combinations thereof.